PROJECT SUMMARY The overarching goal of this proposal is to use bronchiolitis as a case study to advance the science of de- implementation by identifying strategies and processes for reducing over-testing and over-treatment in bronchiolitis that can later be broadly adapted to varied contexts and disease processes. The challenge in bronchiolitis is that providing high-quality, evidenced-based care requires a ?less is more? approach as the non- recommended, outdated, and potentially harmful tests and treatments that most admitted patients receive do not have replacements. Therefore, bronchiolitis which is the most common cause of hospitalization among infants, is an ideal condition to study de-implementation. In her set of projects, Dr. Tyler proposes the innovative application of dissemination and implementation (D&I) science to the unique problem of de-implementation. Within a learning health system called PEDSnet, Dr. Tyler will use the PRISM D&I model as a guide to: 1) use qualitative methods to define contextual factors influencing over-utilization in bronchiolitis from the perspective of healthcare providers, parents, and healthcare organizations, 2) develop a set of pragmatic, feasible, and effective de-implementation strategies for bronchiolitis that includes guidance on how to adapt the strategies to local contexts, and 3) conduct a pilot study to determine the feasibility, acceptability, and de-implementation effectiveness of the de- implementation strategies. As one of the first explorations of contextual factors fostering overuse or enabling successful de-implementation, this study is expected to generate valuable knowledge relevant to de- implementation across diseases and healthcare settings. The results will provide pilot data for a large-scale, pragmatic, randomized-controlled trial of the de-implementation strategies so that ineffective and potentially harmful medical practices are reduced. The applicant, Amy Tyler, MD, MSCS is excellently prepared to complete the proposed research, given her past training and experience. To build upon this experience and progress toward her long-term career goals, Dr. Tyler seeks to use this career development award to achieve investigative independence and advance scientific understanding of effective and generalizable methods for de-implementing potentially harmful tests and treatments. This work will promote guideline concordant, high quality, acute care for pediatric patients, an AHRQ priority population. Dr. Tyler has assembled an internationally-recognized mentorship team with expertise directly related to her training goals in dissemination and implementation science (D&I) (Drs. Dempsey and Glasgow), qualitative research (Drs. Dempsey and Holtrop), and pragmatic clinical trials (Drs. Dempsey and Glasgow). She will conduct the proposed research in the collaborative environment of the University of Colorado Anschutz Medical Campus supported by the Adult and Child Consortium for Health Outcomes Research and Delivery Science D&I Science and Outcomes Research Cores.